Computerized tomographic colography (CTC), a revolutionary new tool, employs virtual reality technology to produce two- and three-dimensional images that permit a thorough and minimally invasive evaluation of the entire colorectal structure. This nascent imaging tool holds promise in screening colorectal neoplasia as its sensitivity, specificity, safety, cost-effectiveness, and patient acceptability, theoretically, may approach the ideal. Given the societal importance of colorectal cancer control and the limitations of currently used screening approaches, there exists a strong rationale to aggressively investigate CTC for a potential screening application. Our laboratory has completed extensive preliminary work on this technology, and has published nearly all peer reviewed clinical studies to date. It is our objective to clinically validate CTC for the detection of colorectal neoplasia. The proposal addresses aspects of central importance to the chemical application of CTC in three inter-related but independent parts that will be conducted in parallel. In Part I, the CTC technique will be optimized by evaluating the use of radiopaque contrast material added to the colonic lavage preparation, as well as the usefulness of prone and supine CT scanning to eliminate problems with retained fluid and collapsed bowel segments. The combined clinical performance of an optimized CTC will then be prospectively compared in blinded fashion to that of the current screening modalities--fecal occult blood testing, flexible sigmoidoscopy, barium enema, and colonoscopy. Patient acceptance for each examination, as well as the cost-effectiveness implications of observed performance outcomes, will be evaluated using a predictive model. In Part II, methods will be studied to improve the efficiency of image displays and interpretation. Methods to be studied include a tissue characterization tool using textual analysis to differentiate stool from polyps, and image display of entire segments of the colon using 3D rendered views of the colon (virtual pathology). In Part III, computerized discrimination and subtraction of stool will be explored. Virtual bowel preparation as a patient-friendly alternative to lavage cleansing will be investigated, in which contrast- tagged stool is electronically purged from the CTC image. The study is fiscally responsible and capitalizes on the abundant clinical and laboratory resources within the Mayo Medical Center. Data generated should provide for a balanced appraisal of the value and practically of this potentially powerful new screening tool.